The objective of the proposed experiments is to determine the neuroendocrine mechanisms linking aggression, social status and stress. In humans and other vertebrates, stress from aggression or low social status results in highly modified behavior and emotional dysfunction, such as depression. A model system with relatively simple behavior and a visible indicator of stress responsiveness, provides a mechanism for studying complex integration of autonomic and limbic systems with brainstem monoamine perikarya and peripheral stress responses. In Anolis carolinensis, a unique sign stimulus, the formation of postorbital eyespots, appears to be directly related to social status. Therefore, altering the formation of the eyespot using either physical or pharmacological manipulations should influence social status. Specific Aims: This proposal will ivestigate four related objectives. The first objective is to determine the relative influence of the eyespot as a social signal. Second, determining the value of the eyespot as a social signal in previously established social hierarchies adds the test of reversal of dominance. The eyespot, as a social signal, may override previously established social status. Third, is determining the relationships among eyespot formation, aggression and monoamine release in hippocampus, testing if in specific nuclei (e.g. hippocampus) 5-HT and DA are inversely related to one another with respect to behavior. Microdialysis will be utilized to measure serotonergic and dopaminergic activity during aggressive interactions. The fourth objective is to learn if there is a direct reciprocal regulation of hippocampal dopamine and serotonin.